Link adaptation is an important feature in modern wireless communication systems. Utilizing link adaptation, a first communication device, e.g., a base station (BS), adapts the modulation and/or coding parameters for the radio channel conditions when communicating with a second communication device, e.g., a mobile station (MS). Link adaptation systems require knowledge of the channel conditions at the transmitting device. Channel information can be measured at a receiving device, e.g., the MS and fed back to the BS, or vice versa.
Generally, there are two methods for adapting modulation and/or coding parameters. Both methods involve measuring a carrier to interference-plus-noise ratio (CINR) at the receiving device, e.g., the MS. The first method involves the MS transmitting the measured CINR to the BS in the form of what is referred to as a “physical” CINR (PCINR) report. The second method is called an effective CINR (ECINR) report, and involves the MS determining adjustments to the modulation and/or coding parameters, and transmitting the adjustments to modulation and/or coding parameters to the BS.
Most existing CINR measurement methods are transmission scheme and detection scheme dependent. CINR for single antenna systems, like single-input single-output (SISO) systems, is simply defined as the signal-to-noise ratio at the receiver. For multiple antenna systems, e.g., multiple-input multiple-output (MIMO) systems, the CINR is dependent on the channel condition, transmission scheme, and detection scheme. In addition, current CINR measurements are not accurate in certain situations. For example, in the WiMAX™ communication standard, CINR measurement for MIMO spatial multiplexing with maximum likelihood detection is defined according to channel capacity. However channel capacity is an ideal quantity that does not account for systemic imperfections such as frequency offset or clock/time offset.
Accordingly, a technique for generic CINR measurement, independent of transmission scheme, detection scheme, and one that accounts for systemic imperfections in a wideband wireless communication system would be useful for making adjustments in the wireless communication system modulation and/or coding parameters.